Structure of a Typical Dicot Embryo

The zygote develops into an embryo at the micropylar end of the embryo sac. During syngamy, it is produced when a male gamete joins an egg cell. The embryonal axis, cotyledons, and embryonal axis are all present in the seed (one or two). At the two extremities of the embryonal axis, there is a radicle and a plumule. 

Dicot embryo

Dicot seeds are seeds that have two embryonic leaves, or cotyledons. 

1. Dicot seeds comprise a single embryo surrounded by two cotyledons and an embryo axis. Previously, all angiosperms or flowering plants were categorised as dicots. 

2. Seed pods in dicot plants vary in size, shape, and quantity because dicot seed pods can have any number of chambers. Dicot seed pods often contain more seeds than monocot seed pods.

3. The seeds of most dicots are symmetrical and can be separated into two parts. The endosperm in dicots is commonly reduced, and in some cases completely absent. 

4. The shape of the seed varies between species and can be used to distinguish between them. Peas and beans, for example, are differentiated by the shape of their seeds. 

5. Dicot seeds come in a variety of sizes, as the group includes a variety of plants ranging from shrubs to herbs to woody trees.

6. Dicot seeds can be distinguished further by the absence of extra sheaths surrounding the embryo.

7. Dicots are not a monophyletic group because their plants do not have a common ancestor. 

Structure of dicot embryo

1. Dicotyledonous or dicot seeds include peas, almonds, and cashews.

2. Dicots are another name for dicotyledons. Previously, all flowering plants, or angiosperms, were separated into these groups. The seed has two embryonic cotyledons, thus the name dicotyledons. To date, around 200,000 species of dicotyledons have been found.

3. The embryo of a dicotyledonous seed consists of an embryo axis and two cotyledons. The inflated look of cotyledons is because they serve as a food reserve for the developing seedling. The embryo axis is divided into two parts. The plumule is the piece at the upper end that produces the shooting point, while the radicle is the portion at the lower end that makes the root tip. The seed coat is a protective shell that surrounds the entire substance. Two layers make up the seed coat: testa on the outside and tegmen on the inside. Furthermore, a structure known as the hilum connects the seed to the fruit.

4. Apples, plums, and peaches are examples of dicot seeds. 

Development of dicot embryo

When the zygote divides transversely, a two-celled proembryo is generated. The basal cell is closest to the micropyle, while the terminal cell is further away. 

To generate a lengthy suspensor, the basal cell undergoes many transverse divisions. By dividing longitudinally twice, the terminal cell divides into four cells. The terminal cell’s four-celled stage is referred to as the quadrant stage. The quadrant stage’s four cells now divide transversely to form an octant stage with eight cells divided into two layers of four cells. The stem tip and cotyledons are formed in the lower tier, while the hypocotyl is formed in the higher tier. 

Periclinal division occurs in the octant cells, resulting in the formation of eight outer and eight inner cells. The dermatogen is made up of the eight outer cells, which divide the anticlinal and grow into the epidermis. The periblem and plerome are formed by the inner cells. The periblem gives way to the cortex, while the plerome gives way to the stele. The basal cell divides multiple times to generate a six- to ten-cell long suspensor. The hypophysis is the suspensor cell nearest to the developing embryo. The root cap, epidermis, and cortex of the root are formed by repetitive divisions of the hypophysis. 

The curvature of the cotyledons is caused by further hypocotyl and cotyledon expansion. At this stage, the embryo seems to be shaped like a horseshoe. The stem tip is terminal in the mature embryo, and the two cotyledons are positioned laterally. 

Conclusion

The fundamental distinction between monocot and dicot embryos is that monocot embryos have only one cotyledon, whereas dicot embryos have two cotyledons. Angiosperms, or flowering plants, are divided into two groups: monocots and dicots. They are the most successful and diverse plant species on the planet. The structure of monocots and dicots differs as well. Stems, roots, leaves, flowers, and seeds come in a variety of shapes and sizes.